The heterogeneity of the Tahe fractured?vuggy reservoir is strong, and the fluid flow state is complex. The flow and waterflooding mechanisms of high?asphaltene heavy oil remain poorly understood, posing significant challenges to the effective implementation of water injection strategies. Based on a visualization model of fractured?vuggy reservoirs, experimental investigations were carried out on the flow and displacement behavior of heavy oil with different viscosities. The relationship between the flow resistance coefficient of asphaltene containing heavy oil and the viscosity and flow rate was established, and dynamic quantification of oil saturation in different vuggys was achieved through image recognition. The characteristics of waterflooding of high asphaltene heavy oil in fractured?vuggy reservoirs and the influence mechanisms of heavy oil viscosity, fractures, and water injection rate were clarified. The results indicate that the viscosity of heavy oil increased from 59 mPa ? s (medium viscosity) to 1 090 mPa ? s (extra viscosity), the apparent threshold pressure gradient of heavy oil in the fracture cavity increased by one order of magnitude, the flow resistance coefficient increased by three times, and the waterflooding recovery rate decreased by 9.6 percentage points. Increased heavy oil viscosity also reduced the number of vugs affected by waterflooding, thereby increasing the remaining oil volume in attic configurations, localized high points, and along cavity walls. The scale, length, and spatial distribution of crack width have a greater impact on the flow direction of waterflooding heavy oil, and are stronger than the gravity differentiation of oil and water. Appropriately increasing the water injection rate enhances the ability of water flooding to spread and break through small?scale fractures.

Revealing the micro-and meso-scale hydrogen?induced crack propagation mechanism of high-strength pipeline steel holds significant engineering value for ensuring the safety of hydrogen energy transportation. In this study, a ferrite-cementite interface model with Bagaryatskii crystallographic relationship was established for the pearlite structure formed by eutectoid ferrite (α-Fe) and cementite (Fe₃C) in ferrite?pearlite pipeline steel. Combined with Voronoi polygon polycrystalline model and cohesive zone model, the effects of hydrogen atom number fractions, grain size and cementite termination surface on the mechanical properties of pipeline steel in a hydrogen environment were systematically analyzed. The results indicate that at the micro scale, with the increase of hydrogen atom number fractions, the critical interfacial tension of pipeline steel decreases obviously, which decreases by about 3.10% and 7.50% respectively at 2.5% and 5.0% hydrogen atom number fractions, and the fracture energy also shows a downward trend. The order of cementite termination surface according to crack resistance is C-Fe > C-C > Fe-Fe > Fe-C. At the meso-scale, the increase of hydrogen atom number fractions (5.0%) leads to a decrease of 8.39% in the critical stress intensity factor（K_IC） and an increase of 12.06% in the crack length. When the grain size is refined from 16 μm² to 4 μm², the K_IC increases by 31.38% and the crack length decreases by 17.30%. The influence of the termination surface is consistent with the microscopic results. This research provides a theoretical reference for the intrinsic safety evaluation and adaptability analysis of ferrite?pearlite pipeline steel in hydrogen environment.